1. Field of the Invention
The present invention relates to a brush-less motor, a control circuit thereof and the like, relates to a constitution used in a vacuum pump of, for example, a vacuum pump of a magnetic bearing type turbo-molecular pump or the like or a magnetic bearing spindle or the like.
2. Description of the Related Art
Conventionally, starting a brush-less motor is carried out as follows.
There is a brush-less motor having a rotor having a permanent magnet of two poles and three motor phase windings for generating a magnetic field for rotating the rotor at its surrounding.
In such a brush-less motor, there is a constitution in which as a sensor-less brush-less motor control circuit which is not provided with a sensor for detecting positions of magnetic poles, current for driving the motor is made to flow to two motor windings in three motor windings to thereby rotate a rotor, by rotating the rotor, positions of magnetic poles of the rotor are detected from induced electromotive force produced in a remaining one of the motor windings and based on the positions of the magnetic poles, the current of the motor winding is successively switched.
An explanation will be given of an example of the above-described conventional brush-less motor control circuit in reference to FIG. 8 and FIG. 9.
FIG. 8 is a conceptual view representing a brush-less motor of a three-phase all wave system. A rotor 150 is provided with a permanent magnet of two poles. There are arranged U-phase, V-phase and W-phase motor windings 151U, 151V and 151W around the rotor. Current is made to flow to excite two of the motor windings and the rotor 150 is rotated by attractive force of magnetic force thereof. Excited ones of the motor windings 151U, 151V and 151W are successively switched in accordance with positions of the magnetic poles of the rotor 150 to thereby continue rotating the rotor 150. The positions of the magnetic poles are detected by detecting voltage induced in a remaining one of the motor windings which is not excited.
As shown by FIG. 9, there are six kinds of driving voltage vectors outputted to the motor windings 151U, 15V and 151W of the brush-less motor of the three-phase all wave system.
The driving voltage vector when current is made to flow from the U-phase motor winding to the V-phase motor winding is defined as driving voltage vector 1, the driving voltage vector when current is made to flow from the U-phase motor winding to the W-phase motor winding is defined as driving voltage vector 2, the driving voltage vector when current is made to flow from the V-phase motor winding to the W-phase motor winding is defined as driving voltage vector 3, the driving voltage vector when current is made to flow from the V phase motor winding to the U-phase motor winding is defined as driving voltage vector 4, the driving voltage vector when current is made to flow from the W-phase motor winding to the U-phase motor winding is defined as driving voltage vector 5, the driving voltage vector when current is made to flow from the W-phase motor winding to the V-phase motor winding is defined as driving voltage vector 6 and hereinafter, the driving voltage vectors will be distinguished from each other by the numerals.
The numerals of the driving voltage vectors are indicated by circling the numerals in FIG. 9.
Further, current which is made to flow from the V-phase motor winding to the W-phase motor winding is described as current in Vxe2x86x92W direction and the like.
The control circuit of the motor generates one pulse per rotation of the rotor 150 in synchronism with the rotation of the rotor 150 from detected positions of magnetic poles. The pulse is inputted to a PLL (Phase Lock Loop) circuit, not illustrated, and the PLL circuit generates six pulses each having a period six times as much as rotation of the rotor 150. In synchronism with the six pulses, the above-described six driving voltage vectors are successively switched to thereby continue rotating the rotor 150. That is, the positions of the magnetic poles of the rotor 150 are detected from voltage of the motor winding constituting conductless phase and the voltage vectors outputted to the motor windings 151U, 151V and 151W are switched while carrying out a feedback by the detected values.
Meanwhile, in order to lock (operate) the PLL circuit, at least about 20 Hertz is needed for a frequency of an input signal. That is, unless the rotor 150 is rotated by about 20 times per second, the PLL circuit cannot be operated.
Conventionally, until the motor is started and a rotational number of the rotor 150 is increased to a rotational number capable of locking the PLL circuit, the respective driving voltage vectors are switched by an open loop. That is, the voltage vectors applied to the motor windings 151U, 151V and 151W are initially switched successively at a low speed near to DC (direct current) without carrying out a feedback operation at all, the switching speed is gradually accelerated and the rotor is made to attract and follow thereto to thereby accelerate the rotor to the rotational number capable of locking the PLL circuit.
As a control circuit of a brush-less motor for switching driving voltage vectors by generating pulses synchronized with a multiplied value of a rotational number of a rotor by using a PLL circuit in this way, there is invention of Japanese Patent Laid-Open No. 47285/1996. According to the invention, positions of magnetic poles are detected by Hall sensors and driving voltage vectors are controlled by a feedback control.
Three Hall sensors are arranged at a surrounding of magnetic poles of a rotor at angular intervals of 120xc2x0, when the rotor is rotated at a low speed by which a PLL circuit cannot be locked in starting a motor, driving voltage vectors are controlled by detected signals by the three Hall sensors, when a rotational number of the rotor reaches a rotational number capable of locking the PLL circuit, the PLL circuit generates multiplied synchronized pulses each having a period three times as much as the rotational number of the rotor from the detected signals of one of the Hall sensors and the driving voltage vectors are switched by the multiplied synchronized pulses.
Further, the technology is applicable also by detecting counter electromotive voltage generated at the motor windings and produced by rotating the rotor without using the Hall sensors. That is, the technology is applicable to a motor drive circuit free of Hall sensors using a PLL circuit.
A conventional sensor-less brush-less motor is controlled by a control circuit operated as follows.
The control circuit of the sensor-less brush-less motor controls currents flowing in motor windings by a feedback control while detecting positions of magnetic poles of a rotor. The positions of the magnetic poles of the rotor are detected by detecting voltage induced in the motor windings by rotating the rotor, that is, induced electromotive force. For example, in the case of a three phase brush-less motor, voltage is applied to the two motor windings and voltage induced in the remaining conduct less phase is detected. Further, based on the positions of the magnetic poles detected by the voltage, the two motor windings to be applied with voltage are determined and voltage is applied thereto. At the occasion, the induced electromotive force of the motor winding constituting the conductless phase is detected and the positions of the magnetic poles are detected thereby. The motor is driven by continuously carrying out the process.
FIG. 20 illustrates diagrams indicating timings of detecting the positions of the magnetic poles of the control circuit in the conventional sensor-less brush-less motor. Waveforms 201a, 201b and 201c are waveform diagrams of voltage induced in a certain motor winding. As mentioned later, FIG. 20(a) shows a case in which a phase of a rotating field produced by current of the motor winding is more advanced than a phase of rotating the rotor, FIG. 20(b) shows a case in which the phases of both coincide with each other and FIG. 20(c) shows a case in which the phase of the rotating field is more advanced than the phase of the rotor.
The positions of the magnetic poles are detected by sampling intersections 203a, 203b and 203c of imaginary neutral point potentials 202a, 202b and 202c and the waveforms 201a, 201b and 201c. 
The control circuit is provided with a driving mode of outputting voltage to the motor winding and a sampling mode of not outputting voltage thereto. As shown by FIG. 20, during a time period of ⅔ of a period of rotating the rotor, voltage is outputted to the motor winding in the driving mode and during a remaining time period of ⅓ of the period, voltage is not outputted thereto in the sampling mode. This is for preventing the waveforms 201a, 201b and 201c from being superposed with noise in detecting the positions of the magnetic poles.
The intersections 203a, 203b and 203c are detected in the time period of the sampling mode.
FIG. 20(a) shows the case in which the phase of the rotating field is more advanced than the phase of rotating the rotor and an area surrounded by the waveform 201a and the imaginary neutral potential 202a on the left side of the intersection 201a, becomes smaller than an area surrounded by the waveform 201a and the imaginary neutral potential 202a on the right side of the intersection 201a. FIG. 20(b) shows the case in which the phases of both coincide with each other and the above-described left and right areas become equal to each other. FIG. 20(c) shows the case in which the phase of the rotating field lags behind the phase of the rotor and the area on the left side of the intersection 203c becomes larger than the area on the right side.
The conventional control circuit controls the voltage outputted to the motor winding by a feedback control such that the areas on the left side and the right side of the intersection become always equal to each other as in the intersection 203b. 
Further, when the conventional sensor-less brush-less motor is applied to a vacuum pump of a turbo-molecular pump or the like, the following problem is posed.
There is a case that a motor portion of a turbo-molecular pump is constituted by a DC brush-less motor constituted by a rotor shaft having a permanent magnet and a plurality of pieces of electromagnets arranged at a surrounding of the permanent magnet at predetermined intervals.
However, according to the conventional starting method, when the switching speed of the driving voltage vectors of the motor windings 151U, 151V and 151W is rapidly increased or the load of the rotor 150 is rapidly changed, there is a case in which the rotor 150 cannot follow the magnetic field produced by the motor windings 151U, 151V and 151W and is brought out of phase and fails in staring. Further, when the switching speed of the voltage vectors is increased gradually by taking a long period of time, a long period of time is required of the rotor 150 to reach a rotational number (or speed) capable of locking the PLL circuit. Further, when interruption or the like is caused and restarting is needed before the rotor 150 reaches the rotational number capable of locking the PLL circuit after starting the motor, since the positions of the magnetic poles cannot be detected by the control circuit of the conventional sensor-less brush-less motor, it is necessary to stop the rotor 150 once by direct current braking and thereafter start the rotor 150. Particularly, in the case of a turbo-molecular pump, about one minute is required for accelerating the rotational number of the rotor 150 to reach about 20 rotations per second capable of locking the PLL circuit and therefore, loss of time by the above-described cause is enormous.
Meanwhile, according to the control circuit of the conventional sensor-less brush-less motor, the intersections 203a,203b and 203c must be brought into the sampling mode, for example, when a variation of load is caused in the rotor and the intersections 203a, 203b and 203c are deviated from the sampling mode, there is a case in which the positions of the magnetic poles are disturbed and an out-of-phase state is brought about. Further, there is a case in which noise is superposed on voltage of the motor windings in detecting the magnetic pole of the rotor and the positions of the magnetic poles cannot accurately be detected.
Further, in the case in which the rotor of the brush-less motor is axially supported by a magnetic bearing, for example, when the rotor is subjected to direct current braking in starting to thereby set the magnetic poles to predetermined positions, since there is no friction in the magnetic bearing, there poses a problem that the rotor is vibrated centering on the predetermined position and the vibration is not attenuated swiftly. Further, the magnetic field is rotated slowly by an open loop until the rotational number of the rotor shaft reaches a rotational frequency capable of locking the PLL circuit (rotational number of rotor per unit time, about 20 [Hz] in this case) and therefore, time is taken in starting, further, when the rotational number of the rotor shaft is significantly changed in steady-state operation, there is a case in which the positions of the magnetic poles cannot be detected and out-of-phase is brought about.
It is a first object of the invention to provide a control circuit of a motor detecting the positions of the magnetic poles of the rotor 150 without using sensors even in low speed rotation of 20 rotations per second or lower which has been operated by an open loop conventionally and controlling to switch voltage vectors applied to the motor windings by a feedback control by using the detected value.
It is a second object of the invention to provide a control apparatus of a sensor-less brush-less motor capable of properly controlling current of motor windings by accurately detecting positions of magnetic poles of a rotor even when rotational speed of the rotor is significantly changed by a variation of load or the like or noise is superposed on voltage of the motor windings.
It is a third object of the invention to provide a control circuit of a sensor-less brush-less motor, a sensor-less brush-less motor apparatus and a vacuum pump apparatus using the motor capable of controlling to switch a magnetic field by a feedback control by detecting magnetic poles of a rotor even at, low speed rotation of 20 rotations per second or lower and capable of carrying out a feedback control by accurately detecting positions of the magnetic poles even when rotational speed of the rotor is significantly changed or noise is superposed on voltage of motor windings.
In order to achieve the first object, according to an aspect of the invention, there is provided a control circuit of a brush-less motor wherein comprising a rotor having magnetic poles, a first motor winding comprising at least two motor windings for rotating the rotor, a second motor winding comprising at least one motor winding for detecting a position of the rotor, rotor rotating means for rotating the rotor by making a current flow to the first motor winding, voltage acquiring means for acquiring a voltage induced in the second motor winding, magnetic pole position acquiring means for acquiring magnetic pole positions of the magnetic poles from the voltage acquired by the voltage acquiring means, and current switching means for switching the current such that a direction of a magnetic field by the first motor winding is changed in accordance with the magnetic pole positions acquired by the magnetic pole position acquiring means (first constitution).
According to the first constitution, the positions of the magnetic poles are acquired by detecting the voltage induced in the second motor winding in which current for rotating the rotor is not made to flow and therefore, the magnetic field operated to the rotor can be controlled by a feedback control without using sensors for detecting the positions of the magnetic poles.
Further, according to another aspect of the invention, in order to achieve the first object, there is provided a control circuit of a brush-less motor comprising a rotor having magnetic poles, a plurality of motor windings for rotating the rotor, rotor rotating means for rotating the rotor by making currents flow to at least two of the plurality of motor windings in which phases and magnitudes of voltage drop caused by inductances of the motor windings are equal to each other, voltage difference acquiring means for acquiring a difference between voltages supplied to the two motor windings having the equal phases and magnitudes of voltage drop, magnetic pole position acquiring means for acquiring positions of the magnetic poles based on the difference between the voltages acquired by the voltage difference acquiring means, and winding current switching means for switching the currents in accordance with the positions of the magnetic poles acquired by the magnetic pole position acquiring means (second constitution).
According to the second constitution, the positions of the magnetic poles are acquired by monitoring the voltages of the motor windings outputting driving voltage vectors. When the driving voltage vectors are selected pertinently, the voltage drop by the inductances appearing in the motor windings can be equalized between the two motor windings. By taking the difference therebetween, the voltage drop can be eliminated and the positions of the magnetic poles can be acquired from a signal thereof. Further, the driving voltage vectors can be controlled by a feedback control from the positions of the magnetic poles.
Further, according to other aspects of the invention, in order to achieve the first object, there are provided the control circuit of a brush-less motor further comprising an integrator for removing electric noise superposed on the voltage acquired by the voltage acquiring means of the first constitution (third constitution) and the control circuit of a brush-less motor further comprising an integrator and a direct current cut filter for removing electric noise superposed on the difference between the voltages acquired by the voltage difference acquiring means of the second constitution (fourth constitution).
By weakening the noise by integrating the voltage of the voltage acquiring means in the third constitution and the voltage difference by the voltage difference acquiring means in the fourth constitution by the integrators, signals embedded in the noise can be detected. Further, the direct current cut filter is connected in series with an input side of the integrator for cutting a direct current component of a signal inputted to the integrator and preventing the direct current component of the signal inputted to the integrator from being integrated.
Further, according to another aspect of the invention, in order to achieve the first object, there is provided the control circuit of a brush-less motor according to any one of the first constitution through the fourth constitution, wherein further comprising a sensor for detecting the magnetic pole positions of the rotor, rotational number detecting means for detecting a rotational number of the rotor from the magnetic pole positions detected by the sensor, and rotational number determining means for determining whether the rotational number detected by the rotational number detecting means is equal to or larger than a predetermined rotational number, wherein when the rotational number is equal to or larger than the predetermined rotational number, the currents of the plurality of motor windings are switched in accordance with the magnetic pole positions detected by the sensor, and when the rotational number detected by the rotational number detecting means is less than the predetermined rotational number, the currents of the motor windings are switched in accordance with the magnetic pole positions acquired by the magnetic pole position acquiring means.
According to the control circuit, by the control circuits of constitutions of the first constitution through the fourth constitution, when the rotor is started and the rotational number reaches the predetermined value, the motor can smoothly shift to steady-state operation. Further, when the rotational number is equal to or larger than the predetermined rotational number, the sensor for detecting the positions of the magnetic poles is used and therefore, the circuit constitution becomes simpler than that in the case of operating the motor without a sensor.
Further, according to the invention, when the rotor is axially supported by a magnetic bearing, in sampling a displacement signal of a position of a shaft of the magnetic bearing, noise superposed on a sampling signal can be reduced by cutting the currents of the motor windings or preventing the currents from being switched.
Thereby, an error of a detected position of the shaft of the magnetic bearing can be reduced and abnormal sound or vibration from the magnetic bearing can be restrained from occurring.
Further, when the rotational number of the rotor exceeds the predetermined value, by switching the motor to a motor drive system for generating motor drive pulses by utilizing a PLL circuit, the operation can be switched to the normal operation.
According to another aspect of the invention, in order to achieve the second object, there is provided a control circuit of a sensor-less brush-less motor wherein comprising a rotor having magnetic poles, a plurality of motor windings for rotating the rotor, current supplying means for supplying currents to the plurality of motor windings, magnetic flux acquiring means for acquiring an interlinking magnetic flux of at least one of the motor windings by the magnetic poles, and magnetic pole position acquiring means for acquiring positions of the magnetic poles from a change in the interlinking magnetic flux acquired by the magnetic flux acquiring means, wherein the current supplying means switches the currents of the motor windings based on the positions of the magnetic poles acquired by the magnetic pole position acquiring means (fifth constitution).
Further, as a variation of the fifth constitution, the magnetic flux acquiring means may be constituted to acquire a difference between interlinking magnetic fluxes of two of the motor windings by the magnetic poles.
According to the control circuit of the sensor-less brush-less motor or the aspect or the invention, rotational positions of the magnetic poles of the rotor can be acquired at arbitrary time in operating the motor and therefore, even when the rotational number of the motor is significantly changed by a variation in load of the motor, the currents of the motor windings can properly be controlled.
Further, the magnetic flux acquiring means according to the fifth constitution may comprise first acquiring means for acquiring an inter-cable voltage of predetermined two of the motor windings, second acquiring means for acquiring voltage drop by a synthesized resistance of resistances of the predetermined two motor windings and resistances of cables connecting a power supply apparatus constituting the current supplying means and the motor windings, third acquiring means for acquiring a difference between the currents of the two predetermined motor windings multiplied by values of inductances of the two predetermined motor windings, integrated value acquiring means for subtracting a value acquired by the second acquiring means from a value acquired by the first acquiring means and integrating it, and subtracting means for subtracting a value acquired by the third acquiring means from a value acquired by the integrated value acquiring means (sixth constitution).
Further, as a variation of the sixth constitution, the magnetic flux acquiring means according to the fifth constitution may comprise first integrated value acquiring means for acquiring a value produced by integrating an inter-cable voltage of the predetermined two motor windings overtime, second integrated value acquiring means for acquiring a value produced by integrating over time, voltage drop by a synthetic resistance of the resistances of the predetermined two motor windings and the resistances of cables connecting a power source apparatus constituting the current supplying means to the motor windings, third integrated value acquiring means for acquiring a value produced by integrating over time, voltage drop by inductances of the predetermined two motor windings, and subtracting means for subtracting the value acquired by the second integrated value acquiring means and the value acquired by the third integrated value acquiring means from the value acquired by the first integrated value acquiring means.
According to the sixth constitution and the variation of the sixth constitution, when the integrated values are acquired, the signal is integrated by using the integrators and therefore, noises superposed on the signal are canceled and the signal having small noise can be provided. Therefore, rotation of the motor can be monitored while operating the motor.
Further, a value of the synthesized resistance used in the sixth constitution can be acquired by synthesized resistance value acquiring means including direct current supplying means for supplying a direct current to the two predetermined motor windings; and first calculating means for calculating the value of the synthesized resistance by dividing a value of the inter-cable voltage by a current value of the direct current.
The method is carried out by conducting the direct current to the predetermined two motor windings, for example, before starting the motor.
Further, the inductance used in the sixth constitution can be acquired by inductance acquiring means including high frequency current supplying means for supplying high frequency currents to the two predetermined motor windings, inter-cable voltage value acquiring means for acquiring the value of the inter-cable voltage of the two motor windings when the high frequency currents are supplied thereto, and second calculating means for acquiring a value of the inter-cable voltage value divided by the current values of the high frequency currents, frequencies of the high frequency currents and a predetermined constant.
The method can be carried out by conducting the high frequency current to a degree to which the rotor cannot follow, to the predetermined two motor windings, for example, before starting the motor. The above-described predetermined value is 2xcfx80.
Further, the inductance used in the sixth constitution can be acquired by inductance acquiring means, the inductance acquiring means comprising rotor rotating means for rotating the rotor by switching the currents of the motor windings by an open loop, sampling means for sampling integrated values acquired by the first integrated value acquiring means before and after switching the currents of the motor windings, current peak value acquiring means for acquiring peak values of the values of the currents supplied to the predetermined two motor windings, and third calculating means for dividing an absolute value of a difference between the first integrated values before and after switching the currents acquired by the sampling means by the current peak values acquired by the current peak value acquiring means.
According to the method, the rotor is rotated by the open loop to some degree of rotational number and at that occasion, the inductances are calculated by a magnitude of a stepped difference appearing in a waveform produced by the first integrating means in switching the motor drive current.
Further, the synthesized resistance and the inductances used in the fifth constitution or the sixth constitution can be acquired by providing assumed magnetic flux acquiring means for acquiring interlinking magnetic fluxes of the two predetermined motor windings by using assumed values of the resistance values and assumed values of the inductances and correcting means for correcting the assumed values of the resistance values and the assumed values of the inductances from inter-cable voltage values of the two predetermined motor windings when the rotor is rotated by a predetermined angular speed by the rotor rotating means, inter-cable voltages of the two predetermined motor windings when supply of the currents of motor windings is stopped and the rotor is run freely by the predetermined angular speed, a signal provided by the assumed magnetic flux acquiring means when supply of the currents is stopped, and a phase difference of the signal provided by the assumed magnetic flux acquiring means when the supply of the currents is restarted.
First, the interlinking magnetic fluxes generated in the motor windings are calculated by assumed synthetic resistance value and inductances, thereby, the assumed synthetic resistance value and inductances are corrected. By repeating the process several times, successively corrected synthetic resistance value and inductances approach true values.
Further, according to another aspect of the invention, in order to achieve the third object, there is provided a control circuit of a sensor-less brush-less motor wherein comprising magnetic flux signal acquiring means for acquiring a magnetic flux signal by integrating a voltage difference between predetermined two phases in a plurality of motor windings for rotating a rotor having magnetic poles in which phases and magnitudes of voltage drop by inductances of the motor windings are equal to each other, first drive timing acquiring means for acquiring a drive timing of a driving voltage vector constituting a portion of outputable driving voltage vectors from the magnetic flux signal acquired by the magnetic flux signal acquiring means, first driving voltage vector outputting means for outputting the portion of the driving voltage vector in synchronism with the drive timing acquired by the first drive timing, second drive timing acquiring means for acquiring output timings of the outputable driving voltage vectors by multiplying the timing provided from the magnetic flux signal acquired by the magnetic flux signal acquiring means, second driving voltage vector outputting means for outputting the outputable driving voltage vectors in synchronism with the drive timing acquired by the second drive timing acquiring means, and selecting means for selecting the first driving voltage vector outputting means and the second driving voltage vector outputting means (seventh constitution).
Further, according to another aspect of the invention, in order to achieve the third object, there is provided a control circuit of a sensor-less brush-less motor comprising current supplying means for supplying currents to a plurality of motor windings for rotating a rotor having magnetic poles, inter-cable voltage acquiring means for acquiring an inter-cable voltage of predetermined two motor windings in the plurality of motor windings in which phases and magnitudes of voltage drop by inductances of the motor windings are equal to each other, resistance amount correcting means for correcting a change of a voltage by a synthesized resistance of resistances of the predetermined two motor windings and resistances of connection cables for connecting a power supply apparatus constituting the current supplying means and the motor windings from the inter-cable voltage acquired by the inter-cable voltage acquiring means, magnetic flux signal acquiring means for acquiring a magnetic flux signal by integrating the inter-cable voltage corrected by the resistance amount correcting means, reactance amount correcting means for correcting a change amount by reactances of the predetermined two motor windings among the magnetic flux signal acquired by the magnetic flux signal acquiring means, magnetic pole position acquiring means for acquiring positions of the magnetic poles from the magnetic flux signal corrected by the reactance amount correcting means, and correction nullifying means for nullifying at least the reactance amount correcting means in the resistance amount correcting means and the reactance amount correcting means to be prevented from correcting the magnetic flux signal, wherein when a rotational number of the rotor is equal to or smaller than a predetermined rotation, at least the reactance amount correcting means is nullified by the correction nullifying means and the current supplying means supplies the currents to the predetermined two motor windings by a first mode switching the currents flowing in the predetermined two motor windings based on the positions of the magnetic poles acquired by the magnetic pole position acquiring mean, and wherein when the rotational number of the rotor is larger than the predetermined rotation, the currents are supplied to the motor windings by a second mode of switching the currents of the motor windings based on the positions of the magnetic poles acquired by the magnetic pole position detecting means without using the correction nullifying means (eighth constitution).
In the eighth constitution, there can be constructed a constitution in which the current supplying means makes small currents flow in the plurality of motor windings in accordance with a predetermined order during a predetermined time period when a mode is switched from the first mode to the second mode (ninth constitution).
The seventh constitution or the eighth constitution can be constituted to further comprise direct current cutting means capable of switching a first cutoff frequency and a second cutoff frequency of a frequency larger than the first cutoff frequency for removing a direct current component superposed on the magnetic flux signal, and switching means for switching the first cutoff frequency and the second cutoff frequency of the direct current cutting means (tenth constitution).
In the tenth constitution, there can be constructed a constitution in which the switching means sets the cutoff frequency of the direct current cutting means to the first cutoff frequency during a predetermined time period from when the rotor is started and switches the cutoff frequency of the direct current cutting means to the second frequency when the predetermined time period has elapsed.
Further, according to another aspect of the invention, in order to achieve the third object, there is provided a brush-less motor apparatus characterized by being constructed of a control portion comprising a motor portion comprising a rotor having magnetic poles, a first motor winding comprising at least two motor windings for rotating the rotor, and a second motor winding comprising at least one motor winding for detecting a position of the rotor, rotor rotating means for rotating the rotor by making a current flow in the first motor winding, voltage acquiring means for acquiring a voltage induced in the second motor winding, magnetic pole position acquiring means for acquiring magnetic pole positions of the magnetic poles from the voltage acquired by the voltage acquiring means, and current switching means for switching the current such that a direction of a magnetic field by the first motor winding is changed in accordance with the magnetic pole positions acquired by the magnetic pole position acquiring means (eleventh constitution).
Further, according to another aspect of the invention, in order to achieve the third object, there is provided a brush-less motor apparatus characterized by being constructed by a control portion comprising a motor portion comprising a rotor having magnetic poles, and a plurality of motor windings for rotating the rotor, rotor rotating means for rotating the rotor by making currents flow to at least two motor windings in the plurality of motor windings in which phases and magnitudes of voltage drop by inductances of the motor windings are equal to each other, voltage difference acquiring means for acquiring a difference between voltages operated to the two motor windings having the equal phases and equal magnitudes of the voltage drop, magnetic pole position acquiring means for acquiring positions of the magnetic poles from the difference between the voltages acquired by the voltage difference acquiring means, and winding current switching means for switching the currents in accordance with the positions of the magnetic poles acquired by the magnetic pole position acquiring means (twelfth constitution).
Further, according to another aspect of the invention, in order to achieve the third object, there is provided a sensor-less brush-less motor apparatus characterized by a control portion comprising a motor portion comprising a rotor having magnetic poles, and a plurality of motor windings for rotating the rotor, current supplying means for supplying currents to the plurality of motor windings, magnetic flux acquiring means for acquiring an interlinking magnetic flux of at least one of the motor windings by the magnetic poles, and magnetic pole position acquiring means for acquiring positions of the magnetic poles from a change in the interlinking magnetic flux acquired by the magnetic flux acquiring means, wherein the current supplying means switches the currents of the motor windings based on the positions of the magnetic poles acquired by the magnetic pole position acquiring means (thirteenth constitution).
Further, according to another aspect of the invention, in order to achieve the third object, there is provided a sensor-less brush-less motor apparatus wherein comprising a rotor having magnetic poles, a plurality of motor windings for rotating the rotor, magnetic flux signal acquiring means for acquiring a magnetic flux signal by integrating a voltage difference between predetermined two phases in the plurality of motor windings in which phases and magnitudes of voltage drop by inductances of the motor windings are equal to each other, first drive timing acquiring means for acquiring a drive timing of a driving voltage vector constituting a portion of outputable driving voltage vectors from the magnetic flux signal acquired by the magnetic flux signal acquiring means, first driving voltage vector outputting means for outputting the portion of the driving voltage vector in synchronism with the drive timing acquired by the first drive timing acquiring means, second drive timing acquiring means for acquiring output timings of the outputable driving voltage vectors by multiplying the timing provided from the magnetic flux signal acquired by the magnetic flux signal acquiring means, second driving voltage vector outputting means for outputting the outputable driving voltage vectors in synchronism with the drive timings acquired by the second drive timing acquiring means, and selecting means for selecting the first driving voltage vector outputting means and the second driving voltage vector outputting means (fourteenth constitution).
Further, according to another aspect of the invention, in order to achieve the third object, there is provided a vacuum pump apparatus wherein comprising an exterior member one end of which is formed with an intake port and other end of which is formed with an exhaust port, a rotor axially supported rotatably by a magnetic bearing or a mechanical type bearing at inside of the exterior member, a motor for rotating the rotor, and a stator arranged at the inside of the exterior member, wherein the motor is constituted by the brush-less motor apparatus according to the eleventh constitution or the twelfth constitution or the sensor-less brush-less motor apparatus according to the thirteenth constitution or the fourteenth constitution.